This is an old hack (1997) and does not
accomplish much, but it is fun! Silicosis of L0pht
(sili@l0pht.com) wrote the original
exploit code for *nix systems and someone else ported it to NT/2000/XP
based systems. Although it's been out there for a long time, it still works
on every HP printer/JetDirect box I have seen. What the HP display hack
allows you to do is set the text that displays on the little LCD panel of an
HP printer. It accomplishes this over the network by sending packets to a
JetDirect box hooked to the printer (or built into it).

The first thing you need to do is find
out the IP or hostname of the JetDirect box that services the printer. You
can do this in one of at least three ways. The first way is by hitting the
little test button on the JetDirect box that's connected to the printer. If
the JetDirect card is built in you may have to go through the menus and
choose "Print Configuration". Another way is to go into your "Printers and
Faxs" settings, right click and bring up the properties of the printer in
question, and look under the Ports tab for the hostname (npi******). Once
you have this information it's easy to run Silicosis ' little hack.

To run it from Windows just use the
following syntax: hpnt Hostname Message
Windows Example:

If you want to
run it from Linux download the source code at the bottom of this page and
compile it using gcc. The syntax is the same as the Windows version. Below
is an example of how to compile and run it: